20-atom gold cluster

Figure 12. Promoting effect of moisture on CO oxidation over an eight atoms gold cluster on MgO single crystal [47].

Figure 13. CO oxidation over 13 atoms gold clusters having different three-dimensional structures supported on Mg(OH)2 [30].

The only ten-atom gold cluster, [Au10Cl3(PCy2Ph)6]+, has structure (10c) with approximate D3h symmetry.306 The structure is an Au-centred trigonal prism of Au atoms (each with one radial Au—P bond), with Au—Cl groups capping the prismatic faces. The Au-centred Au6 chair of other gold clusters is present. 

Link, S. El-Sayed, M. A. Schaaff, T. G. Whetten, R. L. Transition from nanoparticle to molecular behavior a femtosecond transient absorption study of a size-selected 28-atom gold cluster. Chem. Phys. Lett. 2002, 356, 240-246. 

Link, S., Beeby, A., et al. Visible to Infrared Luminescence from a 28-Atom Gold Cluster. The Journal of Physical Chemistry B,106(13), 3410-3415 (2002). 

Andersen, H.H., Brunelle, A., Della-Negra, S., Depauw, J., Jacquet, D., Le Beyec, Y. (1998) Giant metal sputtering yields induced by 20-5000 keV atom gold clusters. Phys. Rev. Left.,5/1,5433-5436. 

In [155], the influence of relativistic effects on adsorption of Hg and Cn on gold was investigated on the example of small ad-atom-gold clusters modelling adsorption at the on-top and hollow positions (Fig. 31). Relativistic effects were shown to define the trend to a decrease in Eb(M-Au ) from Hg to Cn, even though they increase Et(M-Au, both in the Hg and Cn systems, especially at the hollow position due to the involvement of the 6d(Cn) AOs in bonding. This makes the difference in Eb(M-Au ) between Hg and Cn very small. Relativistic effects were shown to decrease the distance of the ad-atom to the surface, in all the cases. 

M. A. Omaiy, M. A. Rawashdeh-Omaiy, C. C. Chusuei, J. P. Fackler and P. S. Bagus, Electronie strueture studies of six-atom gold clusters,/ Chem. Phys., 2001, 114, 10695-10701. 

Visible to infrared luminescence from a 28-atom gold cluster, S. Link, A. Beeby, S. FitzGerald, M. A. El-Sayed,T. G. Schaaff, R. L. Whetten, J. Phys. Chem. B 2002, 106, 3410. 

Figure 11.18 Catalytic activity of gold clusters deposited on MgO for CO oxidation as a function of the number of atoms. Gold clusters were deposited on defect-rich MgO(lOO) films. (Reproduced with permission from Springer [88].)...

Other reducing agents like Ti(7y6-toluene)2 have also been used. Addition or removal of gold atoms from clusters can frequently be accomplished (Figure 4.44). 

It came as a surprise, however, that Aug prefers a trigonal planar D3h structure in the gas phase [16] and is not octahedral as one might assume, suggesting that gold clusters do not follow the usual pattern of typical Lennard-Jones, Morse or Gupta systems, which all favor a maximum number of close atom-atom contacts. The preferred planarity of small gold cluster compounds is due to relativistic effects [17]. 

Akola, J. and Hakkinen, H. (2006) Density functional study of gold atoms and clusters on a graphite 0001 surface with defects. Physical Review B - Condensed Matter, 74, 165404-1-165404-9. 

Ford, M.J., Soule de Bas, B. and Cortie, M.B. (2007) Stability of the teti ahedral motif for small gold clusters in the size range 16-24 atoms. Materials Science and Engineering B, 140, 177-181. 

Another example that small clusters exhibit high catalytic activity is seen in Au/Mg(OH)2 prepared by DP [31]. Only when gold clusters are composed of 13 atoms they exhibit high catalytic activity for CO oxidation even... 

The second example is 55 atoms cluster reported by Boyen s group of University of Ulm [104]. They measured XPS spectra for gold clusters with different diameters... 

The presence of both single gold atoms and gold clusters, evident in Figure 3(b), indicates that the deposition flux is largely atomic or very small clusters as expected from the process gas pressure. 

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